1. Field of the Invention
The present invention relates to a stereoscopic image pickup apparatus arranged to perform stereoscopic photography by leading right and left images having parallax (parallactic images) alternately in a time-series manner to one image sensor.
2. Description of Related Art
Heretofore, there has been proposed, for example, in Japanese Laid-Open Patent Application No. Hei 6-327036, a stereoscopic image pickup apparatus arranged to perform stereoscopic photography by leading images having parallax for right and left eyes alternately in a time-series manner to one and the same area of one image sensor by means of a liquid crystal shutter. FIG. 11 shows such a stereoscopic image pickup apparatus. The stereoscopic image pickup apparatus shown in FIG. 11 is composed of two right reflecting mirrors 2 and 4, two left reflecting mirrors 1 and 3, a liquid crystal shutter 7 arranged to be drivable in a divisional manner in area, and a photographic lens 5. The liquid crystal shutter 7 is disposed in the vicinity of an entrance pupil of the photographic lens 5 on the object side of the photographic lens 5, so that right and left images having parallax can be alternately made incident on one image sensor.
In the conventional stereoscopic image pickup apparatus shown in FIG. 11, the reflecting mirrors 1 and 2 are disposed aslant with respect to the reflecting mirrors 3 and 4 in such a way that light beams emitted from one point, on an optical axis, of the object S meet at one point of the image plane 6 after having passed through the right and left pupils. Such a conventional stereoscopic image pickup apparatus will be described here with reference to FIGS. 2 to 4.
FIG. 2 is an optical path diagram which is equivalent to a case where an object located at a short distance is photographed by the above-mentioned conventional stereoscopic image pickup apparatus. Referring to FIG. 2, principal planes RLH and LLH of right and left photographic lenses RL and LL are parallel with right and left image pickup planes RFPxe2x80x2 and LFPxe2x80x2, respectively, and the principal planes RLH and LLH of the right and left photographic lenses RL and LL are slanting with respect to an object plane OBP. Optical axes of the right and left photographic lenses RL and LL are denoted by AXR and AXL, respectively. In this case, the distances from the principal planes RLH and LLH of the right and left photographic lenses RL and LL to the object plane OBP vary with the positions (the right end, the center and the left end) on the object plane OBP. Accordingly, right and left images RFP and LFP formed respectively on the right and left image pickup planes RFPxe2x80x2 and LFPxe2x80x2 are caused to have trapezoidal distortions which differ in directivity.
Therefore, if a right-side image RFP and a left-side image LFP are superposed on each other in such a way that points on the optical axes AXR and AXL of the right and left photographic lenses RL and LL coincide with each other, as shown in FIG. 3, an image deviation ULD in the vertical direction and an image deviation RLD in the horizontal direction would occur at diagonal positions of rectangular images RFP and LFP. Thus, if an image deviation in the vertical direction is large, it becomes difficult for right and left images to fuse with each other at the time of observation, and, if an image deviation in the horizontal direction is large, depth perception would vary between the central image portion and the right and left end image portions at the time of observation.
FIG. 4 is an explanatory diagram for explaining a case where a stereoscopic image photographed by the arrangement shown in FIG. 2 is displayed on an image display device DSP, such as a liquid crystal display device or a CRT display device, and is then observed by the viewer with the right eye REYE and the left eye LEYE. Referring to FIG. 4, the image deviation RLD in the horizontal direction shown in FIG. 3 causes a stereoscopic image OBIM of an object to be observed in a curved manner away from the image display device at the marginal portion of the image.
As mentioned in the foregoing, the stereoscopic image pickup apparatus configured with the so-called intersection method, in which the right and left optical axes of the photographing optical system are made to intersect at an arbitrary distance, has such a theoretical problem as described above in photographing a short-distance object.
It is an object of the invention to realize a stereoscopic image pickup system capable of photographing a short-distance stereoscopic image, in which no trapezoidal distortion occurs in stereoscopically photographing a short-distance object, and marginal portions of right and left images easily fuse with each other at the time of observation with any unnatural curvature of field not being observed.
To attain the above object, in accordance with a first aspect of the invention, there is provided a stereoscopic image pickup system for obtaining parallactic images of an object, the stereoscopic image pickup system comprising a pair of, first and second, reflecting members each having a reflecting function, a pair of, first and second, amount-of-light control members arranged to respectively vary amounts of transmission of light fluxes coming from the first and second reflecting members alternately in a time-series manner, an optical member arranged to superpose an optical axis of a light flux having passed through the first reflecting member and the first amount-of-light control member and an optical axis of a light flux having passed through the second reflecting member and the second amount-of-light control member on one and the same optical axis, an image sensor for converting a light flux coming from the optical member into an electrical signal, and a controller for causing, on the basis of information on a distance to the object, an image taking-in area of the image sensor to differ between a first image formed on the image sensor by the light flux having passed through the first reflecting member and the first amount-of-light control member and a second image formed on the image sensor by the light flux having passed through the second reflecting member and the second amount-of-light control member.
In accordance with a preferred aspect of the invention, the stereoscopic image pickup system further comprises a pair of front lens units of negative refractive power disposed on a side nearer to the object than the optical member, and a rear lens unit of positive refractive power disposed between the optical member and the image sensor.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup system, the rear lens unit includes a magnification varying lens unit consisting of at least two lens units, and the controller causes, in accordance with the information on the distance to the object and a magnification varying position of the magnification varying lens unit, the image taking-in area to differ between the first image and the second image on the image sensor.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup system, the rear lens unit further includes a lens unit disposed between the optical member and the magnification varying lens unit and arranged to be movable along an optical axis of the rear lens unit so as to compensate for defocusing due to a change of the distance to the object.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup system, the pair of, first and second, amount-of-light control members are disposed between the optical member and one of the pair of front lens units and between the optical member and the other of the pair of front lens units, respectively.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup system, the optical axis of the light flux having passed through the first reflecting member and the first amount-of-light control member and the optical axis of the light flux having passed through the second reflecting member and the second amount-of-light control member are parallel with each other on a side nearer to the object than the pair of, first and second, reflecting members.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup system, the pair of, first and second, reflecting members are arranged to be rotatable around respective predetermined axes, and the controller causes, in accordance with a rotational angle of each of the pair of, first and second, reflecting members and the information on the distance to the object, the image taking-in area to differ between the first image and the second image on the image sensor.
In accordance with a preferred aspect of the invention, the stereoscopic image pickup system further comprises a pair of amount-of-light attenuating members for adjusting an amount of light, between the first reflecting member and the optical member and between the second reflecting member and the optical member, respectively.
In accordance with a preferred aspect of the invention, the stereoscopic image pickup system further comprises a distance detector for detecting the information on the distance to the object.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup system, the controller computes, in accordance with a result of detection provided by the distance detector, an amount of shifting by which the image taking-in area is shifted between the first image and the second image on the image sensor.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup system, the controller performs a shifting action on the image taking-in area between the first image and the second image on the image sensor in synchronism with operations of the pair of, first and second, amount-of-light control members.
In accordance with a preferred aspect of the invention, the stereoscopic image pickup system further comprises a distance detector for detecting the information on the distance to the object, and a magnification varying position detector for detecting a magnification varying position of the magnification varying lens unit.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup system, the controller computes, in accordance with a result of detection provided by the distance detector and a result of detection provided by the magnification varying position detector, an amount of shifting by which the image taking-in area is shifted between the first image and the second image on the image sensor.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup system, the controller performs a shifting action on the image taking-in area between the first image and the second image on the image sensor in synchronism with operations of the pair of, first and second, amount-of-light control members.
In accordance with a preferred aspect of the invention, the stereoscopic image pickup system further comprises a storage device for storing therein an image signal outputted from the image sensor.
Further, to attain the above object, in accordance with a second aspect of the invention, there is provided a stereoscopic image pickup optical system for obtaining parallactic images of an object, the stereoscopic image pickup optical system comprising a pair of front optical units having respective optical axes parallel with each other on the object side and arranged to respectively vary amounts of transmission of light fluxes coming from the object alternately in a time-series manner, an optical member arranged to superpose the respective optical axes of the pair of front optical units on one and the same optical axis, a rear optical unit disposed in such a manner that the superposed optical axes of the pair of front optical units coincide with an optical axis of the rear optical unit, an image sensor for converting a light flux coming from the rear optical unit into an electrical signal, and a controller for varying an image taking-in area of the image sensor in synchronism with varying alternately the amounts of transmission of light fluxes respectively passing through the pair of front optical units.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup optical system, the pair of front optical units include a pair of shutters arranged to respectively vary the amounts of transmission of light fluxes coming from the object alternately in a time-series manner, and the controller controls opening and closing of the pair of shutters.
In accordance with a preferred aspect of the invention, the stereoscopic image pickup optical system further comprises an iris disposed at a position where the respective optical axes of the pair of front optical units are superposed, or disposed in the vicinity of the position.
In accordance with a preferred aspect of the invention, in the stereoscopic image pickup optical system, the rear optical unit includes a plurality of lens units arranged to move along an optical axis thereof for focusing or for variation of magnification.
The above and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.